操作机主运动机构的解耦性研究

巨型重载操作机是极限制造装备技术的重要体现,为了降低操作机的控制难度,研究3种常见锻造操作机主运动机构的解耦性问题。建立3种锻造操作机的运动学模型,并求解机构的速度输入—输出关系矩阵,发现在传统的输出参数定义下,3种操作机的输入始终处于耦合状态。根据实际工作状态重新定义输出参数,在此基础上提出一个新的解耦定义方法。分别单独求解每个动作下的速度的输入—输出关系矩阵,并且利用Matlab仿真验证,发现其中一种操作机的主运动机构是完全解耦的,而另外两种操作机属于部分解耦。从锻造操作机主运动机构的解耦过程来看,重新定义输出是一种直观的解耦方法,该方法为并联机构的解耦提供一种新思路。     

锻造操作机提升机构设计方法

基于螺旋理论并结合工程实际对锻造操作机的构型设计进行系统、深入的研究,构造多种串并联形式的混联结构锻造操作机提升机构构型。这些锻造操作机提升机构的升降和俯仰运动采用平面五杆机构实现,侧移运动采用一种典型DANGO&DIENENTHAL(DDS)锻造操作机的侧移系统实现,大车前进方向的移动和侧摆由悬挂系统实现。所以这些锻造操作机提升机构解耦性能高,均为实际应用中可以考虑的构型。根据实际工程经验可知,锻造操作机的悬挂系统为由前悬挂部分和后悬挂部分组成的并联机构,前悬挂部分由两根对称的悬挂杆组成,后悬挂部分由单根悬挂杆或两根对称的悬挂杆组成。将悬挂并联机构型综合分为后悬挂部分含单根悬挂杆和两根悬挂杆两种情况进行讨论,采用基于螺旋理论的约束综合法,构型得到了四种悬挂并联机构构型,其中三种构型为无过约束机构,应用前景广泛。     

新型3自由度可约移动并联机构的构型及设计

提出了一般可约系统的定义。从研究运动不耦合的3自由度移动并联机构的输入输出关系出发,给出了3自由度可约移动并联机构的定义和判定充要条件。定义了一种新的Gf坐标,利用此坐标给出了可约并联机构的型综合一般过程,并综合出了5种3自由度可约移动并联机构。针对这类机构的特殊性能,以其中一种机构为例,基于机构动平台参考点的工作空间进行了优化设计。     

拔长工艺中锻造操作机液压系统能耗分析

扩展了锻造操作机整机的能量流模型和能耗计算模型,研究了拔长工艺下锻造操作机液压系统的控制特性和能耗特性,得出了液压系统的能耗分布规律,分析了能量浪费的关键环节,为锻造操作机液压控制系统的优化以及节能控制方法的提出提供指导。研究结果表明,锻造操作机液压系统的能耗特性具有如下特点：夹钳上升和旋转动作的能量传递效率较高,均可达60%以上;大车行走动作的能量传递效率仅为17%;夹钳下降时重力势能几乎全部转化为升降控制阀的节流损失;多执行器不同负载与单压力源不能合理匹配会造成巨大的节流损失。     

双锻造操作机大车行走系统控制方法探析

双锻造操作机配合压机联动完成大型高精长轴类锻件的锻造,可以有效提高锻造效率,提升锻件品质。针对双操作机夹持锻件同步行走控制难题,以燕山大学的两台20 kN锻造操作机为研究对象,综合考虑了吊挂系统、大车行走机械和液压系统的特点,搭建了双锻造操作机大车行走系统的数学模型。在此基础上,仿真研究了独立反馈位置同步控制方法、位置速度复合独立反馈同步控制方法和位置速度复合状态差值校正同步控制方法对双操作机大车行走系统控制特性的影响。仿真结果表明,对于动力性能差异较大的两台重载机械手,基于位置速度复合状态差值校正同步控制方法的控制效果最为理想,同时设定操作机A和操作机B的给定位移200 mm、加速度1000 mm/s2时,双操作机大车行走系统的动作响应时间为105 s,同步位置误差为［-0.28 mm,0.02 mm］。研究结果可为双锻造操作机控制提供技术支撑和理论指导,对于提升锻造产品质量和实现锻造生产线的智能控制具有重要意义。     

基于GF集的锻造操作机构型方法

为了发展新型锻造操作机,提出基于GF集的锻造操作机构型方法及其构型法则。阐述一种包含移动项和转动项且转动项转动轴线交于一点的特殊集合GF集的概念及构型特点;研究GF集中移动项对转动项转动轴线位置的影响,提出并证明了移动对转动轴线位置影响定理,基于此定理定义了GF集的求和与求交的运算法则;将锻造操作机要求实现的运动分解为由钳杆提升、俯仰和沿操作机前进方向的运动组成的主运动以及由操作机侧移和侧摆组成的次运动两部分,从这两部分的运动入手,采用GF集方法构造出一系列锻造操作机。从锻造操作机的构型过程来看GF集方法是一种直观的构型方法,该方法为锻造操作机构型提供了一种新思路。     

纳米级精度柔性机器人的设计方法及实现研究

从材料、几何结构、柔性铰链、驱动器、运动与负载及加工等几个方面总结了面向精密作业的柔性机器人设计准则。对柔性机器人的设计方法进行了探讨。以精密作业中的具体应用为例，依据这些设计方法与准则，从机械本体和驱动器控制2个方面详细描述了可实现纳米级精度的3自由度柔性机器人样机设计的具体实现过程，设计结果满足任务要求。     

基于矩阵回路的锻造操作机能量回收及控制参数的设计方法

针对阀控式锻造操作机液压系统能源利用效率低、能耗大的问题,基于液压矩阵回路,利用泵/马达能量传递单元以及矩阵阀组的灵活组合,设计了能量回收液压系统,结合恒定压差的伺服控制方法,实现了对锻造操作机大车行走、夹钳下降两种动作的能量回收,为验证节能特性,进行了仿真和模拟实验。结果表明：夹钳下降动作中,蓄能器回收了重力势能的39.2%;大车行走过程中,蓄能器回收了惯性势能的37.1%;采用能量回收系统后,泵源输出能量比原系统减少约13%。能量回收液压系统及恒定压差伺服控制方法实现了对锻造操作机两种动作的能量回收,为多执行器系统的节能发展提供了指导。     

基于REFOR算法的多输出非线性系统动态参数化建模方法研究

针对多输出非线性系统动态模型的辨识问题,提出一种新的非线性系统动态参数化建模方法,即冗余向前延拓正交（Redundant extended forward orthogonal regression,REFOR）算法。该算法旨在消除传统向前延拓正交（Extended forward orthogonal regression,EFOR）算法因遗漏某些重要模型项而造成所建模型精度较低的问题。首先,基于系统在各工况下辨识所得非线性有源自回归（Non-linear autoregressive with exogenous inputs,NARX）模型,利用REFOR算法统一各模型结构得到模型系数与设计参数间的函数关系,进而建立多输出非线性系统的动态参数化模型。其次,以四自由度非线性系统为例,说明了REFOR算法的优势及其在系统建模中的应用。最后,利用REFOR算法建立悬臂梁的动态参数化模型,并将REFOR预测输出与试验测得输出进行对比,试验结果表明,基于REFOR算法建立的非线性系统动态参数化模型,能准确预测系统的输出响应,为非线性系统建模方法的优化设计提供了理论基础。     

一种新型大推力直线压电作动器

设计了一种新型大推力直线压电作动器,采用螺旋箝位的方式实现对压电叠堆微小位移的累积输出,实现了大推力和长行程。对该种作动器的驱动机理和作动器设计过程中的关键技术问题进行了详细的分析,包括力矩电机的转速设计、上下柔性联轴器的扭转刚度设计、螺母和丝杠之间相关机械参数的设计以及对所选压电叠堆进行性能测试并选择其最佳工作频段。原理样机长为140 mm,最大直径为45mm,重量为0.7 kg,行程为40 mm。在力矩电机转速为300 r／min,压电堆驱动频率为100 Hz时,作动器的最大输出力可达130 N。     

Analytical dynamic solution of a flexible cable-suspended manipulator

Cable-suspended manipulators are used in large scale applications with, heavy in weight and long in span cables. It seems impractical to maintain cable assumptions of smaller robots for large scale manipulators. The interactions among the cables, platforms and actuators can fully evaluate the coupled dynamic analysis. The structural flexibility of the cables becomes more pronounced in large manipulators. In this paper, an analytic solution is provided to solve cable vibration. Also, a closed form solution can be adopted to improve the dynamic response to flexibility. The output is provided by the optimal torque generation subject to the actuator limitations in a mechatronic sense. Finally, the performance of the proposed algorithm is examined through simulations.     

Research on parallel load sharing principle of piezoelectric six-dimensional heavy force/torque sensor

In working process of huge heavy-load manipulators, such as the free forging machine, hydraulic die-forging press, forging manipulator, heavy grasping manipulator, large displacement manipulator, measurement of six-dimensional heavy force/torque and real-time force feedback of the operation interface are basis to realize coordinate operation control and force compliance control. It is also an effective way to raise the control accuracy and achieve highly efficient manufacturing. Facing to solve dynamic measurement problem on six-dimensional time-varying heavy load in extremely manufacturing process, the novel principle of parallel load sharing on six-dimensional heavy force/torque is put forward. The measuring principle of six-dimensional force sensor is analyzed, and the spatial model is built and decoupled. The load sharing ratios are analyzed and calculated in vertical and horizontal directions. The mapping relationship between six-dimensional heavy force/torque value to be measured and output force value is built. The finite element model of parallel piezoelectric six-dimensional heavy force/torque sensor is set up, and its static characteristics are analyzed by ANSYS software. The main parameters, which affect load sharing ratio, are analyzed. The experiments for load sharing with different diameters of parallel axis are designed. The results show that the six-dimensional heavy force/torque sensor has good linearity. Non-linearity errors are less than 1%. The parallel axis makes good effect of load sharing. The larger the diameter is, the better the load sharing effect is. The results of experiments are in accordance with the FEM analysis. The sensor has advantages of large measuring range, good linearity, high inherent frequency, and high rigidity. It can be widely used in extreme environments for real-time accurate measurement of six-dimensional time-varying huge loads on manipulators.     

二自由度基本机构特征状态方程及其应用

提出了二自由度基本机构的特征状态分析方法，并依此建立了二自由度基本机构的数学知识模型。首先定义并归纳了运动功能特征模式，继而针对具体二自由度基本机构输入输出连续运动速度一般方程，提取输入输出运动的特征矢量，并在二元函数级数展开的基础上提取出函数的功能特征值，从而把二自由度基本机构的运动传递单元转化为运动特征变换单元，由此使机构的运动功能分析脱离机构单元本身具体尺度的影响；建立了二自由度基本机构的特征状态方程，进一步讨论了特征矢量、特征状态方程的性质及其运算规则，得到了运动传递特征和性质；研究了数学模型到基础数据的知识转换过程，建立了二自由度基本机构基础知识数据库，为机械系统方案设计提供选型依据。通过实例说明了造型过程及其具体方法。     

一种典型DDS锻造操作机运动学分析

锻造操作机的运动学分析是实现操作机运动控制的基础,鉴于大部分学者仅对典型DANGO&DIENENTHAL(DDS)锻造操作机的主运动机构进行运动学分析,对一种典型DDS锻造操作机的整体机构进行运动学分析。该整体机构是由一个平行四杆机构和一个并联机构组成的串并联形式的混联机构。采用修正的Grübler-Kutzbach公式计算其中并联机构的自由度,计算结果表明并联机构的自由度数多于其主动输入数,所以该并联机构的运动无法直接确定。究其原因是机构中4S闭环的侧摆运动规律不唯一,因此对4S闭环的侧摆运动进行优化分析,利用旋转相似变换得到4S闭环侧摆后其输出件的姿态可用yzy欧拉角描述,从而确定该并联机构的运动。采用yzyy欧拉角描述钳杆的姿态,使得前三个姿态角恰好为4S闭环发生侧摆后其输出件的姿态角,从而很容易地建立该操作机整体机构主动输入与钳杆位姿之间的位置关系。在此基础上对该操作机整体机构进行速度分析,并用ADAMS软件对位置分析和速度分析进行仿真验证。     

Computational parametric analysis and experimental investigations of a compact flexure-based microgripper

This paper presents a flexure-based piezoelectric actuated microgripper for high precision grasping/releasing tasks. The design of the microgripper consists of a three-stage amplification and transmission mechanism, and the parallel grasping technique. A bridge-type mechanism and two sequential lever-type mechanisms are symmetrically connected to amplify the output displacement of the embedded piezoelectric actuator. The parallelogram mechanisms assist in linearizing the output displacement of both jaws of the microgripper. The computational analysis is conducted to investigate the effect of the dimensional parameters on the characteristics of the microgripper. A computational parametric optimization methodology is established to achieve the required attributes of the microgripper. The design optimization resulted in a compact design, a high displacement amplification ratio, and a large output displacement of the microgripper. The experimental studies are conducted to investigate the key characteristics of the microgripper such as the displacement amplification ratio, the output displacement, tracking performance. Further, the parasitic motion, input-end and output-end motion resolution of the microgripper are identified. The experimental results indicate that the compact microgripper can achieve a high displacement amplification ratio and large output displacement with a high positioning accuracy.     

Observer based fault tolerant control for a class of Two-PMSMs systems

In this paper, an observer-based state-feedback fault-tolerant controller is proposed for two coupling permanent magnet synchronous motors (PMSMs) system. The controller compensates the actuator faults and allows the system states to track the reference states corresponding to the output of the original two-PMSMs system. To design such a controller, the information of system actuator faults are required. Then, a robust adaptive observer is designed to estimate the system actuator faults firstly. Next, by setting the reference outputs the equilibrium control inputs and reference speeds are computed based on the mathematic model of the two-PMSMs system. Meanwhile, the variation dynamic model is derived. Additionally, the robust stability of the closed-looped system with fault-tolerant controller is analyzed via the Lyapunov theory and interval matrix. Sufficient stability conditions and the gain matrix of the fault-tolerant controller are obtained by solving the linear matrix inequalities (LMIs). Finally, simulation results are presented to illustrate the effectiveness of the proposed observer and fault tolerant control (FTC) scheme.     

Compliant high-precision E-quintet ratcheting (CHEQR) mechanism for safety and arming devices

Ratchet and pawl mechanisms are used in safety applications to provide mechanical isolation between inputs and an output to insure that extreme environmental conditions do not inadvertently allow an unexpected output. These devices have become smaller and are approaching a size regime where traditional precision components, such as precision bearings and springs, are not available. This paper introduces the compliant high-precision E-quintet ratcheting (CHEQR) mechanism as a means of exploiting the advantages of compliant mechanisms to create safety devices that eliminate the need for bearings and springs. The pseudo-rigid-body model was used to design a mechanism with the desired force-deflection characteristics, and the result is a radical departure from traditional ratchet and pawl mechanisms. Large-scale proof-of-concept prototypes were followed by micro-wire EDM fabrication of precipitation hardened stainless steel devices with flexible segment widths of 50 μm. The device was integrated with a 6 mm ratchet wheel and rotary solenoid actuator.     

Force transmission analyses with dimensionally homogeneous Jacobian matrices for parallel manipulators

To avoid the unit inconsistency problem in the conventional Jacobian matrix, new formulation of a dimensionally homogeneous inverse Jacobian matrix for parallel manipulators with a planar mobile platform by using three end-effector points was presented (Kim and Ryu, 2003). This paper presents force relationships between joint forces and Cartesian forces at the three End-Effector points. The derived force relationships can then be used for analyses of the input/output force transmission. These analyses, forward and inverse force transmission analyses, depend on the singular values of the derived unit consistent Jacobian matrix. Using the proposed force relationship, a numerical example is presented for actuator size design of a 3-RRR planar parallel manipulator.     

机构类型综合设计过程自动求解分析及算法实现

定义了实现运动变换的基本机构元素、集合；应用运动变换矩阵，对类型综合过程进行了描述；建立了便于将基本机构信息转换为数据库中存储形式及分解过程的数据结构；基于建立的数学模型及数据结构，提出了运动变换矩阵分解及自动化求解过程的算法。实现了机械系统类型综合设计的自动化求解，通过一个设计实例验证了算法的可行性及有效性。     

Maximum allowable dynamic load of flexible mobile manipulators using finite element approach

In this paper a general formulation for finding the maximum allowable dynamic load (MADL) of flexible link mobile manipulators is presented. The main constraints used for the proposed algorithm are the actuator torque capacity and the limited error bound for the end-effector during motion on a given trajectory. The accuracy constraint is taken into account with two boundary lines which are equally offset due to the given end-effector trajectory, while a speed-torque characteristics curve of a typical DC motor is used for applying the actuator torque constraint. The finite element method (FEM), which is able to consider the full nonlinear dynamics of mobile manipulators, is applied to derive the kinematic and dynamic equations. In order to verify the effectiveness of the presented algorithm, two simulation studies considering a flexible two-link planar manipulator mounted on a mobile base are presented and the results are discussed.